1. Field of the Invention
This invention relates generally to penile prostheses and more particularly is directed to a prosthesis construction of the semi-rigid type, that is, the type in which the length and diameter are predetermined and fixed, and the proper functioning thereof relies on the ability of the prosthesis when implanted in the corpus cavernosum to change configuration by manipulation of the penis between curved depending positions during micturition and when at rest and an extended straight-line erected position during coitus.
2. Description of the Prior Art
Although the inflatable prosthesis more closely parallels natural function, the semi-rigid prosthesis has remained a viable alternative thereto because of the simplicity of the surgical procedure for implanting the semi-rigid device, the lower cost factor for both surgery and prosthesis, the absence of hydraulic operating parts and the minimal theoretical as well as experienced failure of the implant requiring corrective surgical measures. Recognizing the disadvantages inherent in all semi-rigid prostheses, namely, the inability to change length, diameter and flexural stiffness after implantation, various prior art devices have been suggested, manufactured and implanted in a large number of patients, each form of device having features directed to minimize the practical effects of such inherent characteristics.
Several of these semi-rigid prostheses are designed to assume the straight-line erected state but with varying degrees of flexibility as, for example, the Small-Carrion prosthesis disclosed in U.S. Pat. No. 3,893,456, granted July 8, 1975. This construction requires special underwear or other means to retain the penis out of its erected position in daily living. Finney et al. U.S. Pat. No. 4,066,073, granted Jan. 3, 1978, utilizes a rod having axially arrayed sections of various flexural properties. A proximal section suitable for positioning adjacent the pubis is medium stiff in flexure. A longer distal portion, positioned in the corpus cavernosum, is stiffer than the proximal section and a very flexible hinge portion separates the two. The stiff proximal and distal portions are intended to provide desired stiffness to the penis while the hinge portion is intended to permit the penis to be conveniently and easily bent at its base. The intended improvement by Finney et al over Small-Carrion may be offset by problems with thrust during coitus due to the softness of the hinge. Timm et al. U.S. Pat. No. 3,987,789, granted Oct. 26, 1976, provides the plastic body of the prosthesis with a malleable rod portion enabling the implanted penis to be bent and twisted into a variety of shapes which will be retained until reshaped by further bending. The disclosure calls for a rod of nickel-titanium alloy either solid or of stranded filaments. The rod proved unsatisfactory by breaking after repeated bending. This problem was corrected by utilizing a stranded wire made of nearly pure silver, the use of which is reported by Udo Jonas and Gunther H Jacobi in the Journal of Urology, Vol. 123, June 1980, pages 865-14 867. This silicone-silver prosthesis, although reported in the Jonas et al article as having the characteristic of not fatiguing, breaking or hardening under continuous bending, nevertheless, is capable of bending or twisting into undesirable shapes. Having no resiliency whatsoever, once bent, the penis with this implant remains in such undesirable shape, perhaps resembling a corkscrew, until manually reshaped. This can conceivably occur during coitus.
One of the difficulties encountered in both the perineal and dorsal surgical approaches is the size determination and the insertion of the elongated prosthesis into the entire length of the corpus cavernosum through the longitudinal incision along a midportion thereof. This can now only be accomplished by painstaking and time consuming manipulation and bending of a midportion of the prosthesis at an acute angle in order to insert one end into the crus and the other end into the corpus of the pendulus penis to the base of the glans, not necessarily in that order.
It is therefore apparent that to further minimize the inherent disadvantages of the semi-rigid prosthesis by eliminating the hereinbefore mentioned problems and drawbacks of prior art devices as well as to provide prosthesis constructions requiring smaller incisions and facilitating sizing and insertion will satisfy a present need in the management of male impotency where the use of an implant is indicated.